Support DeepSeek reasoning_content field

[tadamcz]

reasoning_content：The content of the CoT, which is at the same level as content in the output structure.

https://api-docs.deepseek.com/guides/reasoning_model

We'd need to store that in appropriate Inspect data structures.

[jjallaire]

This could be added to the ModelOutput class.

[tadamcz]

ChatCompletionChoice, I think, rather than directly on ModelOutput? If you haven't got anyone working on this yet, I can take a crack at it

[jjallaire]

Sorry, yes. ChatCompletionChoice is the right container. I'm wonder if this actually belongs on ChatMessageAssistant then? (as then UIs which deal with lists of messages could show reasoning_content?)

[tadamcz]

I'm wonder if this actually belongs on ChatMessageAssistant then?

Yes, it's debatable. Let me play around with the DeepSeek API and think about it some more. Then I'll open a PR. Might not get to it this week though.

[tadamcz]

Blocked because the DeepSeek API has been very difficult to access in the last few days

[menhguin]

hello, i already have a barebones implementation on deepseek on my fork based off the grok and openai implementations. unfortunately yes, chat API barely works nowadays let alone reasoning for me to test things.
https://github.com/menhguin/inspect_ai/blob/main/src/inspect_ai/model/_providers/deepseek.py

[tadamcz]

Feel free to PR the change if you think it's ready

[jjallaire]

PR here: #1229